About twenty years ago MARTÍNEZ proposed some new genera for the accommodation of a number of aberrant South American aphodiid beetles, until then placed in Euparia LePeletier & Serville. In 1951 he referred two species, Euparia costulata Harold and E. ovalis A. Schmidt, to his genus Lomanoxia, recognizable i.a. by having the sides of the elytra acutely inflexed. As these scarabs are exceedingly rare in collections, I was delighted at finding specimens referable to Lomanoxia among some material collected from the nests of leafcutting ants in Surinam; one represents a species new to science. My unsuccessful efforts to trace the type of Euparia costulata Harold in the Paris museum were compensated by the recovery of additional specimens of Lomanoxia, one of these, from northwestern Argentina, representing a second undescribed species. These new species are described below; in addition, the known species being incompletely or erroneously characterized, a re-description of these is believed to be opportune.The new Lomanoxia from Surinam adds to the list of Eupariini collected with ants. Lomanoxia costulata as well as representatives of Euparia sensu stricto, Euparixia Brown, Myrmecaphodius Martínez, Iarupea Martínez, and Cartwrightia Islas were already on this list (see below). The beetles are assumed to feed upon the debris accumulated in and around the nests of their hosts. Most specimens of the recently described Euparixia moseri Woodruff & Cartwright, however, were taken from fungus-gardens of Atta texana Buck. Meanwhile, of the ecology of eupariine scarabs found with ants we know hardly more than a hundred years ago, when HAROLD (1870: 23) wrote: “Ob nähere Beziehungen zwischen den Ameisen und diesen ihren Gästen bestehen, namentlich ob letztere ihre Verwandlung in den Nestern durchmachen, bleibt noch zu ermitteln.”